Mercury cadmium telluride (HcCdTe) has found use as a semiconductor in such applications as forward-looking infrared (FLIR) receptors. In conjunction with this, an interest has developed in fabricating integrated circuits in layers of mercury cadmium telluride, the fabricating techniques including etching processes.
Mercury cadmium telluride is a very fragile material. It cannot take much stress mechanically, and, in order to avoid dislocations and fusion, needs to be kept at temperatures below 100.degree. C. Highly energetic etching processes, such as plasma or afterglow discharges, may not be used on mercury cadmium telluride surfaces in the way that they are used on more sturdy semiconductor materials such as silicon.
The etching of metals by organic radicals has been studied. As early as 1929, Paneth proved the existence of organic free radicals in pyrolytic experiments by their reaction on metallic mirrors of lead, antimony, zinc and bismuth. F. Paneth and W. Hofeditz, Chem. Ber. 62, 1335; Paneth F. and H. Loleit, J. Chem. Soc. 366 (1935). C. Haag and H. Suhr have reported the etching of indium, germanium, tin, lead, antimony, bismuth and zinc by methyl radicals and partially by phenyl radicals in Plasma Chemistry and Plasma Processing, Vol. 6, p. 197 (1986). However, the application of organic free radicals as etchant species to workpieces or layers of mercury cadmium telluride is not straightforward, because of the above-described fragility and temperature problems of this material in energetic environments. A need has therefore arisen to create organic free radicals for etching a surface of mercury cadmium telluride in such a way that the mercury cadmium telluride workpiece will not be unduly stressed, but which at the same time will result in a useful etching process.